diff --git a/ChangeLog.md b/ChangeLog.md
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--- /dev/null
+++ b/ChangeLog.md
@@ -0,0 +1,5 @@
+# Revision history for argdict
+
+## 0.1.0.0  -- YYYY-mm-dd
+
+* First version. Released on an unsuspecting world.
diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright (c) 2018, Cale Gibbard, Ali Abrar
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Cale Gibbard, Ali Abrar nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/Setup.hs b/Setup.hs
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--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/constraints-extras.cabal b/constraints-extras.cabal
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--- /dev/null
+++ b/constraints-extras.cabal
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+name:                constraints-extras
+version:             0.1.0.0
+synopsis:            Utility package for constraints
+license:             BSD3
+license-file:        LICENSE
+author:              Cale Gibbard, Ali Abrar
+maintainer:          maintainer@obsidian.systems
+copyright:           Obsidian Systems LLC
+build-type:          Simple
+extra-source-files:  ChangeLog.md
+cabal-version:       >=1.10
+
+library
+  exposed-modules:     Data.Constraint.Extras, Data.Constraint.Extras.TH
+  other-extensions:    CPP, ExistentialQuantification, FlexibleInstances, GADTs, LambdaCase, MultiParamTypeClasses, QuasiQuotes, StandaloneDeriving, TypeFamilies, TypeOperators, ConstraintKinds, TemplateHaskell
+  build-depends:       base >=4.9 && <4.11, constraints >= 0.9 && < 0.10, template-haskell >=2.11 && <2.12
+  hs-source-dirs:      src
+  default-language:    Haskell2010
diff --git a/src/Data/Constraint/Extras.hs b/src/Data/Constraint/Extras.hs
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--- /dev/null
+++ b/src/Data/Constraint/Extras.hs
@@ -0,0 +1,26 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE ExistentialQuantification #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE ConstraintKinds #-}
+
+module Data.Constraint.Extras where
+
+import Data.Constraint
+
+-- | Provides proof of the existence of a constraint on a GADT
+class ArgDict f where
+  type ConstraintsFor (c :: * -> Constraint) f :: Constraint
+  argDict :: ConstraintsFor c f => f a -> Dict (c a)
+
+type Has c f = (ArgDict f, ConstraintsFor c f)
+
+-- | Allows explicit specification of constraint implication
+class Implies1 c d where
+  implies1 :: c a :- d a
diff --git a/src/Data/Constraint/Extras/TH.hs b/src/Data/Constraint/Extras/TH.hs
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--- /dev/null
+++ b/src/Data/Constraint/Extras/TH.hs
@@ -0,0 +1,53 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE TemplateHaskell #-}
+module Data.Constraint.Extras.TH where
+
+import Data.Constraint.Extras
+import Control.Monad
+import Data.Constraint
+import Data.Semigroup
+import Language.Haskell.TH
+
+deriveArgDict :: Name -> Q [Dec]
+deriveArgDict n = do
+  ts <- gadtResults n
+  c <- newName "c"
+  let xs = map (AppT (VarT c)) ts
+      l = length xs
+      constraints = foldl AppT (TupleT l) xs
+  [d| instance ArgDict $(pure $ ConT n) where
+        type ConstraintsFor $(varT c) $(pure $ ConT n) = $(pure constraints)
+        argDict = $(LamCaseE <$> matches)
+    |]
+  where
+    matches :: Q [Match]
+    matches = do
+      x <- newName "x"
+      reify n >>= \case
+        TyConI (DataD _ _ _ _ cons _) -> pure $ concat $ flip map cons $ \case
+          GadtC [name] _ (AppT (ConT _) (VarT _)) ->
+            [Match (ConP name [VarP x]) (NormalB $ AppE (VarE 'argDict) (VarE x)) []]
+          GadtC [name] _ _ ->
+            [Match (RecP name []) (NormalB $ ConE 'Dict) []]
+          ForallC _ _ (GadtC [name] _ (AppT (ConT _) (VarT _))) ->
+            [Match (ConP name [VarP x]) (NormalB $ AppE (VarE 'argDict) (VarE x)) []]
+          ForallC _ _ (GadtC [name] _ _) ->
+            [Match (RecP name []) (NormalB $ ConE 'Dict) []]
+          NormalC name [(_, AppT (ConT _) (VarT _))] ->
+            [Match (ConP name [VarP x]) (NormalB $ AppE (VarE 'argDict) (VarE x)) []]
+          a -> error $ "deriveArgDict matches: Unmatched 'Dec': " <> show a
+        a -> error $ "deriveArgDict matches: Unmatched 'Info': " <> show a
+
+gadtResults :: Name -> Q [Type]
+gadtResults n = reify n >>= \case
+  TyConI (DataD _ _ _ _ cons _) -> fmap concat $ forM cons $ \case
+    GadtC _ _ (AppT (ConT _) (VarT _)) -> return []
+    GadtC _ _ (AppT _ (AppT (ConT _) (VarT _))) -> return []
+    GadtC _ _ (AppT _ typ) -> return [typ]
+    ForallC _ _ (GadtC _ _ (AppT (ConT _) (VarT _))) -> return []
+    ForallC _ _ (GadtC _ _ (AppT _ (AppT (ConT _) (VarT _)))) -> return []
+    ForallC _ _ (GadtC _ _ (AppT _ typ)) -> return [typ]
+    _ -> return []
+  a -> error $ "gadtResults: Unmatched 'Info': " <> show a